Fix python 3 errors

[itziakos]

Make sure that the pythonapi functions have the right signature and cast the input values to the right types

fixes issue #51

[codecov-io]

Codecov Report

Merging #52 into master will increase coverage by 0.31%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master      #52      +/-   ##
==========================================
+ Coverage   88.08%   88.39%   +0.31%     
==========================================
  Files          38       38              
  Lines        1007     1017      +10     
  Branches       92       94       +2     
==========================================
+ Hits          887      899      +12     
+ Misses         83       81       -2     
  Partials       37       37

Impacted Files	Coverage Δ
win32ctypes/core/ctypes/_common.py	86.36% <100%> (+2.15%)	⬆️
win32ctypes/core/ctypes/_advapi32.py	89.79% <100%> (ø)	⬆️
win32ctypes/pywin32/win32api.py	87.5% <71.42%> (+0.4%)	⬆️
build/lib/win32ctypes/core/ctypes/_advapi32.py	83.33% <0%> (ø)	⬆️
build/lib/win32ctypes/pywin32/win32api.py	87.3% <0%> (+0.41%)	⬆️
build/lib/win32ctypes/core/ctypes/_common.py	85.71% <0%> (+13.49%)	⬆️

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